The present invention is directed to a full speed animated graphic display specifically designed for a CRT of a personal computer where computer speed is not normally suitable for displaying true animation graphics. The speed of most personal computers allows complete change of the display about twice per second. For true animation, thirty complete changes of display are needed. Also of prime concern is the ability of the artist to use the system to build new animation scripts, without further intervention by the programmer. The animation scripts require control of the background (the still part of the picture at any given instant) and the foreground (the moving part at any instant), clearing the screen, repeating part of a script, display timing, pauses, and other factors.
The invention is suitable for bit-mapped graphic displays having images in which a large part of the image is static, with only a limited amount of movement. As the percentage of the image that is dynamic increases, the invention becomes progressively unsuitable, due to limitations on the computer's ability to maintain a visually acceptable speed of operation. The invention is applicable only to memory-mapped graphics, where a given pixel on the graphics screen in represented in a given memory location in computer memory (RAM). Depending on the number of colors available, each pixel may typically require one byte, a half-byte, two bits, one bit, or some other unit of storage.
U.S. Pat. No. 3,937,878 (Judice) discloses a bi-level (two color) graphics display system primarily concerned with a dithering process which produces gray-scale images. Typically, bi-leveled systems are on/off and do not have the capability for gray tones. In Judice, each display cell is given a dither threshold value. If the signal of any given picture element is greater than the dither threshold value, then that cell is turned on. Otherwise, it is left off. As a result of this dithering process, various shades of gray appear in the reproduced image. The technique is applied to images received from a video camera. In contrast, the present invention is useful with any number of colors. The present invention separates the image development and projection processes. The artist controls the development and projection via a command file and combinations of still images he has created. Judice's technique of dithering is not applicable to the present invention. The present invention treats each color as distinct and unrelated to any other. Pixel colors and animation are produced by replacement of pixel color values rather than from threshold values.
Accordingly, an object of the invention is to provide a method and programming of computer functions on a personal computer to provide true, full-speed animated displays on a CRT.
Another object of the invention is to provide for a full-speed simulated visual display for a personal computer comprising a developer program for developing an animation file and a projector program for projecting the animated file wherein only the projector program may be run during display for fast operation and full speed animation.
Still another object of the invention is to provide a simulated visual display for a personal computer wherein a different animation script may be created by inputting a new series of still image files in accordance with commands and parameters specified by an artist and without intervention by the programmer.